The required transfer in four weeks of all of the Bush White House's electronic mail messages and documents to the National Archives has been imperiled by a combination of technical glitches, lawsuits and lagging computer forensic work, according to government officials, historians and lawyers.

Federal law requires outgoing White House officials to provide the Archives copies of their records, a cache estimated at more than 300 million messages and 25,000 boxes of documents depicting some of the most sensitive policymaking of the past eight years.

But archivists are uncertain whether the transfer will include all the electronic messages sent and received by the officials, because the administration began trying only in recent months to recover from White House backup tapes hundreds of thousands of e-mails that were reported missing from readily accessible files in 2005.

The risks that the transfer may be incomplete are also pointed up by a continuing legal battle between a coalition of historians and nonprofit groups over access to Vice President Cheney's records. The coalition is contesting the administration's assertion in federal court this month that he "alone may determine what constitutes vice presidential records or personal records" and "how his records will be created, maintained, managed, and disposed," without outside challenge or judicial review.

Eventual access to the documentary record of the Bush presidency has been eagerly anticipated by historians and journalists because the president and his aides generally have sought to shield from public disclosure many details of their deliberations and interactions with outside groups.

"We are worried," said Arnita A. Jones, executive director of the American Historical Association, which sued the White House several years ago seeking wider access to presidential records than President Bush had said in a 2001 executive order that he wanted the government to provide. "There is a context that is not reassuring," she said.

The National Archives and Records Administration is supposed to help monitor the completeness of the historical record but has no enforcement powers over White House records management practices. Speaking of the missing e-mails, Archives' general counsel Gary M. Stern said in an interview last week that "we hope and expect they all will exist on the system or be recoverable," even in coming weeks. "We can't say for sure."

White House spokesman Scott M. Stanzel said last week that "we are making significant progress in accounting for the e-mail records stored on our computer network." But he declined to say how many e-mails remain missing or to predict how long the recovery will take because the issue is the subject of ongoing litigation.

The National Security Archive, a historical research group, and Citizens for Responsibility and Ethics in Government, a nonprofit watchdog organization, filed lawsuits in September 2007 to compel the White House to preserve backup e-mail tapes. In November 2007, U.S. District Judge Henry H. Kennedy Jr. ordered White House officials to preserve such tapes and "not transfer said media out of their custody or control without leave of this court."

In the case of the vice president's records, the White House has promised a different federal judge that it will comply with a Nixon-era law requiring the preservation and transfer of all documents related to the vice president's official duties, but the coalition has drafted a filing for the court on Monday that accuses Cheney of subtly seeking to circumscribe the legal definition of what those official duties encompass to such a degree that he will be able to take home or destroy countless documents related to policymaking that historians want to see.

Anne Weisman, the counsel for the plaintiffs, called Cheney's assertion that only those records related to tasks specially assigned by Bush need to be preserved "a loophole . . . large enough to drive truckloads of documents through." It means, she said, that Cheney would not have to surrender documents related to legislation or "advice he gives the president on his own initiative and the influence he has over the president's decisions."

The scramble to find missing e-mails and copy them in a digital form that the Archives can comprehend amounts to a replay of the confusion that capped the transfer of President Bill Clinton's records at the end of his administration in 2001. Then, a series of defects in the White House e-mail archiving system led to congressional subpoenas and the administration's expenditure of $12 million to recover hundreds of missing e-mails from backup tapes. The effort was not completed until after Clinton left office.

Stanzel said the White House is also still "working to acquire" e-mails involving official government business that were transmitted by presidential aides through accounts operated by the Republican National Committee, a problem also first publicized almost three years ago. "We continue to be in communication with RNC officials about recovering official records," he said without offering details. Such records are subject to the Presidential Records Act, which requires their transfer to the Archives at noon on Jan. 20.

Thomas S. Blanton, the National Security Archive director, said controversy surrounding the last-minute handling of e-mails by retiring presidents -- including intervention by the courts -- is hardly exceptional.

Blanton wrote in a 1995 book that Ronald Reagan tried to order the erasure of all electronic backup tapes during his final week in office; the current president's father struck a secret deal with the U.S. archivist shortly before midnight on his final day in office to seal White House e-mails and take them with him to Texas; and Clinton asserted in 1994 that the National Security Council was not an agency of the government so he could keep its e-mails beyond public reach.

Blanton said last week that "the situation is exponentially worse" under the current administration because the volume of electronic records at stake from Bush's tenure is higher than in previous administrations. If some of the records are manipulated, even for a short while, he said, "the problem and the cost to the taxpayers is going to be exponentially worse, [as well as] the delay and the lag time before journalists and historians are going to be able to see this."

The transfer of some White House records officially got under way a few weeks ago with the first air shipments of documents to a leased warehouse north of Dallas, near the projected site of the Bush library, and the transport by truck of some digital records to a remote Navy research center in the mountains of West Virginia. The bullhorn used by Bush at the World Trade Center site in New York is among the objects set to go to Texas.

At the Navy base, all the electronic data are supposed to be "ingested" by a new electronic system meant to allow such efficient cataloguing, indexing and searching that millions of documents can eventually be provided to researchers and citizens online.

The system, which has been under development for a decade by Lockheed Martin and other contractors at a cost of $67.5 million, will rely on software created after the collapse of Enron, when that company's creditors demanded new tools for quickly sorting its e-mail trove to find damaging information.

But there are obstacles to gaining such ready access to files created by Bush and his appointees. Technical troubles, cost overruns and inadequate funding caused the system to be sharply scaled back at the outset, according to Archives officials and the Government Accountability Office. The result is that it will take years of work -- and an additional $70 million -- to put in place the features that the Archives initially sought.

"The ingestion of Bush data has just begun," said Archives spokeswoman Susan Cooper, adding that she is unsure how smoothly it has gone.

The Archives hopes to finish much of its work on the new archival system by 2013, when by law the Bush White House records can begin to be accessed under the Freedom of Information Act.

But Archivist Allen Weinstein and other officials say they may still face a serious shortage of trained staff: Out of the Archives' 3,000 employees at 40 facilities, only a few are assigned to process requests by historians, citizens and others -- 10 at the Reagan library, eight at the first Bush library and 10 at the Clinton library.

The result has been a steady growth in delays for processing data requests, from a wait of a year and a half in 2001 at the Reagan library to a current wait of six and a half years. The new Bush library is slated to have 18 archivists.

"I tried -- half-whimsically -- to ban the word 'backlog' in favor of discussing NARA's 'surplus' of documents, which sounds better but which remains today an intractable problem," Weinstein said in a recent speech.